1 /* 2 * linux/drivers/devfreq/governor_simpleondemand.c 3 * 4 * Copyright (C) 2011 Samsung Electronics 5 * MyungJoo Ham <myungjoo.ham@samsung.com> 6 * 7 * This program is free software; you can redistribute it and/or modify 8 * it under the terms of the GNU General Public License version 2 as 9 * published by the Free Software Foundation. 10 */ 11 12 #include <linux/errno.h> 13 #include <linux/devfreq.h> 14 #include <linux/math64.h> 15 16 /* Default constants for DevFreq-Simple-Ondemand (DFSO) */ 17 #define DFSO_UPTHRESHOLD (90) 18 #define DFSO_DOWNDIFFERENCTIAL (5) 19 static int devfreq_simple_ondemand_func(struct devfreq *df, 20 unsigned long *freq) 21 { 22 struct devfreq_dev_status stat; 23 int err = df->profile->get_dev_status(df->dev.parent, &stat); 24 unsigned long long a, b; 25 unsigned int dfso_upthreshold = DFSO_UPTHRESHOLD; 26 unsigned int dfso_downdifferential = DFSO_DOWNDIFFERENCTIAL; 27 struct devfreq_simple_ondemand_data *data = df->data; 28 unsigned long max = (df->max_freq) ? df->max_freq : UINT_MAX; 29 30 if (err) 31 return err; 32 33 if (data) { 34 if (data->upthreshold) 35 dfso_upthreshold = data->upthreshold; 36 if (data->downdifferential) 37 dfso_downdifferential = data->downdifferential; 38 } 39 if (dfso_upthreshold > 100 || 40 dfso_upthreshold < dfso_downdifferential) 41 return -EINVAL; 42 43 /* Assume MAX if it is going to be divided by zero */ 44 if (stat.total_time == 0) { 45 *freq = max; 46 return 0; 47 } 48 49 /* Prevent overflow */ 50 if (stat.busy_time >= (1 << 24) || stat.total_time >= (1 << 24)) { 51 stat.busy_time >>= 7; 52 stat.total_time >>= 7; 53 } 54 55 /* Set MAX if it's busy enough */ 56 if (stat.busy_time * 100 > 57 stat.total_time * dfso_upthreshold) { 58 *freq = max; 59 return 0; 60 } 61 62 /* Set MAX if we do not know the initial frequency */ 63 if (stat.current_frequency == 0) { 64 *freq = max; 65 return 0; 66 } 67 68 /* Keep the current frequency */ 69 if (stat.busy_time * 100 > 70 stat.total_time * (dfso_upthreshold - dfso_downdifferential)) { 71 *freq = stat.current_frequency; 72 return 0; 73 } 74 75 /* Set the desired frequency based on the load */ 76 a = stat.busy_time; 77 a *= stat.current_frequency; 78 b = div_u64(a, stat.total_time); 79 b *= 100; 80 b = div_u64(b, (dfso_upthreshold - dfso_downdifferential / 2)); 81 *freq = (unsigned long) b; 82 83 if (df->min_freq && *freq < df->min_freq) 84 *freq = df->min_freq; 85 if (df->max_freq && *freq > df->max_freq) 86 *freq = df->max_freq; 87 88 return 0; 89 } 90 91 const struct devfreq_governor devfreq_simple_ondemand = { 92 .name = "simple_ondemand", 93 .get_target_freq = devfreq_simple_ondemand_func, 94 }; 95